What Are Gallstones? Causes, Types & Risk Factors Explained

What Are Gallstones? A Comprehensive Guide

Gallstones are hardened deposits that form inside the gallbladder — a small, pear-shaped organ located beneath the liver on the right side of the abdomen. The gallbladder's primary function is to store and concentrate bile, a digestive fluid produced by the liver that helps break down dietary fats. When the chemical composition of bile becomes imbalanced, the dissolved substances can crystallise and aggregate into stones.

Gallstones can range dramatically in size — from as small as a grain of sand (1–2 mm) to as large as a golf ball (4–5 cm). Some people develop a single large stone, while others develop hundreds of tiny stones simultaneously. The number, size, and composition of stones influence the symptoms they cause and the treatment required.

In India, gallstones affect an estimated 4–8% of the population, with higher prevalence in northern India (up to 15% in some regions). In urban centres like Bangalore, rising rates of obesity, sedentary lifestyles, and dietary changes are driving an increase in gallstone disease, particularly among younger adults.

Types of Gallstones

1. Cholesterol Gallstones (70–80% of Cases)

Cholesterol gallstones are the most common type in India and worldwide. They are typically yellow-green in colour and composed primarily of undissolved cholesterol. They form when bile contains too much cholesterol relative to bile salts and lecithin — the substances that normally keep cholesterol dissolved.

Conditions that increase cholesterol in bile:

• Obesity and metabolic syndrome
• Rapid weight loss or crash dieting (mobilises cholesterol into bile)
• High-fat, low-fibre diet
• Diabetes and insulin resistance
• Pregnancy (oestrogen increases cholesterol secretion into bile)
• Oral contraceptives and hormone replacement therapy
• Prolonged fasting or total parenteral nutrition

2. Pigment Gallstones (20–25% of Cases)

Pigment stones are dark brown or black and form from excess bilirubin — a yellow pigment produced when the liver breaks down old red blood cells. They are more common in patients with conditions that cause excessive red blood cell destruction.

Black pigment stones are associated with:

• Liver cirrhosis
• Chronic haemolytic conditions (sickle cell disease, thalassemia, hereditary spherocytosis)
• Ileal disease or resection (reduces bile salt reabsorption)

Brown pigment stones are associated with:

• Bile duct infections (cholangitis)
• Parasitic infections (Clonorchis sinensis, Ascaris)
• Biliary stasis from strictures or obstruction

3. Mixed Stones

Mixed stones contain both cholesterol and pigment components. They are actually the most common type found in Indian patients undergoing cholecystectomy, reflecting the mixed dietary and metabolic risk factors prevalent in the population.

How Gallstones Form: The Pathophysiology

The formation of cholesterol gallstones involves three key steps:

Step 1: Bile supersaturation — The liver secretes bile that is supersaturated with cholesterol. This occurs when cholesterol secretion increases (obesity, high-fat diet) or when bile salt secretion decreases (ileal disease, certain medications).

Step 2: Nucleation — Cholesterol crystals begin to form within the bile. This process is accelerated by nucleating factors (mucin glycoproteins, calcium bilirubinate) and inhibited by anti-nucleating factors (apolipoproteins AI and AII). In gallstone patients, the balance tips towards nucleation.

Step 3: Stone growth — Once crystals form, they aggregate and grow within the gallbladder. Impaired gallbladder motility (common in pregnancy, diabetes, and prolonged fasting) allows crystals to accumulate rather than being expelled into the bile duct.

Risk Factors: The Complete Picture

Non-Modifiable Risk Factors

• Gender: Women are 2–3 times more likely than men to develop gallstones, primarily due to oestrogen's effects on bile composition and gallbladder motility
• Age: Risk increases progressively after age 40; gallstones are rare before age 20
• Ethnicity: Higher prevalence in Native Americans, Hispanics, and Northern Indians
• Family history: First-degree relatives have 2–3 times higher risk; specific genetic variants (ABCG5/G8 genes) have been identified
• Pregnancy: Multiple pregnancies significantly increase risk

Modifiable Risk Factors

• Obesity: BMI >30 doubles the risk; BMI >45 increases risk 7-fold
• Rapid weight loss: Losing more than 1.5 kg/week mobilises cholesterol into bile
• Diet: High saturated fat, refined carbohydrates, and low fibre increase risk
• Physical inactivity: Sedentary lifestyle increases risk by 40%
• Medications: Oestrogens, clofibrate, octreotide, ceftriaxone
• Metabolic conditions: Diabetes, hypertriglyceridaemia, Crohn's disease

The Natural History of Gallstones

Understanding what happens to gallstones over time is crucial for treatment decisions.

Silent gallstones (70–80% of cases): Most gallstones are discovered incidentally during ultrasound for another reason. Studies show that only 20–30% of people with silent stones will ever develop symptoms over 20 years. The annual risk of developing symptoms is approximately 1–2%.

Symptomatic gallstones: Once symptoms develop, the risk of further complications (cholecystitis, CBD stones, pancreatitis) increases significantly — approximately 1–3% per year. This is why surgery is recommended for symptomatic stones.

Complications of untreated gallstones:

• Acute cholecystitis — Gallbladder inflammation from cystic duct obstruction (10–15% of symptomatic patients)
• Choledocholithiasis — Stones migrating into the common bile duct (10–15%)
• Gallstone pancreatitis — Stones obstructing the pancreatic duct (3–7%)
• Acute cholangitis — Bile duct infection from CBD obstruction (1–2%)
• Gallbladder cancer — Rare but associated with chronic gallstone disease

Diagnosis

Abdominal Ultrasound (First-Line Investigation)

Ultrasound is the gold standard for diagnosing gallbladder stones, with sensitivity >95% and specificity >99%. It is painless, radiation-free, widely available, and inexpensive. It can detect stones as small as 2 mm and assess gallbladder wall thickness, bile duct diameter, and liver parenchyma.

Blood Tests

• Liver function tests (LFTs): Elevated bilirubin, ALP, and GGT suggest bile duct involvement
• Full blood count (FBC): Elevated WBC suggests cholecystitis or cholangitis
• Serum amylase/lipase: Elevated in gallstone pancreatitis
• C-reactive protein (CRP): Elevated in inflammatory complications

MRCP (Magnetic Resonance Cholangiopancreatography)

MRCP is the gold-standard non-invasive investigation for suspected common bile duct stones. It provides detailed imaging of the entire biliary tree without radiation or contrast injection. Sensitivity for CBD stones >5 mm approaches 95%.

CT Scan

CT is used when complications are suspected (perforation, abscess, pancreatitis). It is less sensitive than ultrasound for gallbladder stones (only 80% of stones are radio-opaque) but excellent for assessing complications.

Endoscopic Ultrasound (EUS)

EUS is the most sensitive investigation for small CBD stones (<5 mm) that may be missed by MRCP. It is performed by passing an ultrasound probe through the mouth into the duodenum.

Treatment Options

Laparoscopic Cholecystectomy (Gold Standard)

Laparoscopic (keyhole) removal of the gallbladder is the definitive treatment for symptomatic gallstones. It is performed through 3–4 tiny incisions (5–10 mm) under general anaesthesia. Most patients go home the same day or the following morning and return to normal activities within 1–2 weeks.

Dr. Adarsh M Patil has performed over 500 laparoscopic cholecystectomies with a complication rate under 0.3% — significantly below the national average.

Robotic Cholecystectomy

For complex cases (severe cholecystitis, previous abdominal surgery, obesity), robotic-assisted surgery using the Da Vinci system offers enhanced precision and 3D visualisation.

ERCP (for CBD Stones)

When stones have migrated into the common bile duct, ERCP (Endoscopic Retrograde Cholangiopancreatography) removes them non-surgically using a flexible endoscope passed through the mouth.

Single-Incision Laparoscopic Surgery (SILS)

For patients concerned about scarring, SILS removes the gallbladder through a single hidden incision in the navel, resulting in a virtually scar-free outcome.

Non-Surgical Options (Limited Role)

Oral dissolution therapy with ursodeoxycholic acid (UDCA) can dissolve small cholesterol stones in 6–24 months, but stones recur in 50% of cases within 5 years. It is only suitable for patients who cannot undergo surgery.

Living Without a Gallbladder

The gallbladder is a storage organ, not essential for digestion. After cholecystectomy, bile flows continuously from the liver directly into the small intestine. Over 90% of patients have no dietary restrictions after 4–6 weeks and lead completely normal lives. A small proportion (10–15%) may experience loose stools after fatty meals initially, which typically resolves within 3–6 months.

When to See a Doctor

Consult Dr. Adarsh M Patil if you experience:

• Recurring upper right abdominal pain, especially after fatty meals
• Nausea and vomiting with abdominal pain
• Indigestion and bloating that doesn't respond to antacids
• Jaundice (yellow skin or eyes) — seek urgent care
• Fever with abdominal pain — seek emergency care

Book a consultation: Call +91 80889 54804 or WhatsApp +91 99724 46882. Apollo Clinic, 1st Floor, 100 Feet Rd, Indiranagar, Bengaluru 560008.

*Medically reviewed by Dr. Adarsh M Patil, MBBS, MS (General Surgery), Fellowship in Advanced Laparoscopy & Bariatric Surgery (Belgium). Consultant General & Laparoscopic Surgeon, Apollo Clinic Indiranagar, Bangalore.*